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Brief Review on Wireless Communications and Networks. Dr. Frank Lee Computer Science Department California Lutheran University 10/26/2005. Outline. Cellular Wireless Networks Wireless Local (Subscriber) Loop Mobile Internet Protocol (IP) Wireless Application Protocol (WAP)

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Brief review on wireless communications and networks l.jpg

Brief Review on Wireless Communications and Networks

Dr. Frank Lee

Computer Science Department

California Lutheran University

10/26/2005


Outline l.jpg
Outline

  • Cellular Wireless Networks

  • Wireless Local (Subscriber) Loop

  • Mobile Internet Protocol (IP)

  • Wireless Application Protocol (WAP)

  • Wireless Local Area Networks (LAN)


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Cellular Systems Terms

  • Base Station (BS) – includes an antenna, a controller, and a number of receivers

  • Mobile telecommunications switching office (MTSO) – connects calls between mobile units


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Steps for a Mobile Cellular Call (Fig. 10.6)

1. Mobile unit initialization: selects the strongest setup control channel

2. Mobile-originated call: sends the number of the called unit on the pre-selected setup channel

3. Paging: The MTSO sends a paging message to certain BSs depending on the called mobile unit number


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Steps for a Mobile Cellular Call (Fig. 10.6)

4. Call accepted: The called mobile unit recognizes its number on the setup channel being monitored and responds to that BS, which send the response to the MTSO

5. Ongoing call: The two mobile units exchange voice or data signals, going through their respective BSs and the MTSO

6. Handoff: If a mobile unit moves out of range of one cell and into the range of another during a connection, the traffic channel has to change (without either interrupting the call or alerting the user) to one assigned to the BS in the new cell


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Cellular Phone Networks – First Generation

  • Provided analog traffic channels

  • Advanced Mobile Phone Service (AMPS)

    • A popular system developed by AT&T

    • In North America, two 25-MHz bands allocated to AMPS

      • One for transmission from base to mobile unit

      • One for transmission from mobile unit to base


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Second-Generation

  • GSM: Global System for Mobile Communications (Europe, 1990)

  • Advantages over first-generation

    • Higher quality signals

    • Higher data rates for supporting digital services

    • Greater channel capacity

    • Better security system

    • Multiple channels per cell

    • Each channel is dynamically shared by a number of users by using CDMA (Code-Division Multiple Access) technology


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Third-Generation

  • Using WCDMA (wide-band CDMA) technology

  • Good voice quality

  • Provide high-speed data rate for motor vehicles over large areas

  • Available to pedestrians standing or moving slowly over small areas

  • Support for 2.048 Mbps for office use

  • Support for both packet switched and circuit switched data services


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Outline

  • Cellular Wireless Networks

  • Wireless Local (Subscriber) Loop

  • Mobile Internet Protocol (IP)

  • Wireless Application Protocol (WAP)

  • Wireless Local Area Networks (LAN)


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Wireless Local Loop (WLL)

  • Fixed wireless access

  • Narrowband – offers a replacement for existing telephony services

  • Broadband – provides high-speed two-way voice and data service

  • Cost – wireless systems are less expensive due to cost of cable installation that’s avoided

  • Installation time – WLL systems can be installed in a small fraction of the time required for a new wired system

  • Selective installation – radio units installed for subscribers who want service at a given time

    • With a wired system, cable is laid out in anticipation of serving every subscriber in a given area


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Outline

  • Cellular Wireless Networks

  • Wireless Local (Subscriber) Loop

  • Mobile Internet Protocol (IP)

  • Wireless Application Protocol (WAP)

  • Wireless Local Area Networks (LAN)


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Operations of Mobile IP (Fig. 12.1)

1. Server X transmits an IP datagram destined for mobile node A.

2. The home agent encapsulates the entire datagram inside a new IP datagram that has the A’s care-of address (foreign agent’s location) in the header, and retransmits the datagram to foreign agent. The use of an outer IP datagram with a different destination IP address is known as tunneling.


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Operations of Mobile IP (Fig. 12.1)

3. The foreign agent strips off the outer IP header, encapsulates the original IP datagram in a network-level PDU (protocol data unit, such as a LAN logic link control frame), and delivers the original datagram to node A across the foreign network.

4. Each IP datagram is sent from A to a router (the foreign agent) on the foreign network for routing to X.

5. The IP datagram from A to X travels directly across the Internet to X, using X’s IP address.


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Mobile IP Applications

  • Enable computers to maintain Internet connectivity while moving from one Internet attachment point to another

  • Mobile – user's point of attachment changes dynamically and all connections are automatically maintained despite the change

  • Nomadic - user's Internet connection is terminated each time the user moves and a new connection is initiated when the user dials back in

    • A new temporary IP address is assigned


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Outline

  • Cellular Wireless Networks

  • Wireless Local (Subscriber) Loop

  • Mobile Internet Protocol (IP)

  • Wireless Application Protocol (WAP)

  • Wireless Local Area Networks (LAN)


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Wireless Application Protocol (WAP)

  • Open standard providing mobile users of wireless terminals access to telephony and information services

    • Wireless terminals include wireless phones, pagers and personal digital assistants (PDAs)

    • Designed to work with all wireless network technologies such as GSM, CDMA, and TDMA

    • Based on existing Internet standards such as IP, WML (wireless markup language), XML, HTML, and HTTP

    • Includes security facilities


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Operations of WAP (Fig. 12.10)

  • Using WAP, a mobile user can browse Web content on an ordinary Web server

  • The Web server provides content in the form of HTML-coded pages that are transmitted using the standard Web protocol stack (HTTP/TCP/IP)

  • The HTML content must go through an HTML filter, which may either be co-located with the WAP proxy or in a separate physical module

  • The filter translates the HTML content into WML content


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Operations of WAP (Fig. 12.10)

5. If the filter is separate from the proxy, HTTP/TCP/IP is used to deliver the WML to the proxy

6. The proxy converts the WML to a more compact form known as binary WML and delivers it to the mobile user over a wireless network using the WAP protocol stack

7. If the Web server is capable of directly generating WML content, then the WML is delivered using HTTP/TCP/IP to the proxy, which converts the WML to binary WML and then delivers it to the mobile node using WAP protocols


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Outline

  • Cellular Wireless Networks

  • Wireless Local (Subscriber) Loop

  • Mobile Internet Protocol (IP)

  • Wireless Application Protocol (WAP)

  • Wireless Local Area Networks (LAN)


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Wireless LAN Applications

  • LAN extension

  • Cross-building interconnect

  • Nomadic access

  • Ad hoc networking


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LAN Extension

  • Wireless LAN linked into a wired LAN on same location

    • Wired LAN

      • Backbone

      • Support servers and stationary workstations

    • Wireless LAN

      • Stations in large open areas

      • Manufacturing plants, stock exchange trading floors, and warehouses


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Cross-Building Interconnect

  • Connect LANs in nearby buildings

    • Wired or wireless LANs

  • Point-to-point wireless link is used

  • Devices connected are typically bridges or routers


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Nomadic Access

  • Wireless link between LAN hub and mobile data terminal equipped with antenna

    • Laptop computer or notepad computer

  • Uses:

    • Transfer data from portable computer to office server

    • Extended environment such as campus


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Ad Hoc Networking

  • Temporary peer-to-peer network set up to meet immediate need

  • Example:

    • Group of employees with laptops convene for a meeting; employees link computers in a temporary network for duration of meeting


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Wireless LAN Requirements

  • Throughput

  • Number of nodes

  • Connection to backbone LAN

  • Service area

  • Battery power consumption

  • Transmission robustness and security

  • Collocated network operation

  • License-free operation

  • Handoff/roaming

  • Dynamic configuration


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Wireless LAN Categories

  • Infrared (IR) LANs

  • Spread spectrum LANs

  • Narrowband microwave



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